How to use AutoValue to parse JSON structured as an array of objects?

Question

I have this JSON body:

[
    {
        "id": 0,
        "field1": "10",
        "field2": "22"
    },
    {
        "id": 1,
        "field1": "11",
        "field2": "23"
    }
]

My pojoItem:

@AutoValue
public abstract class PojoItem{

    @SerializedName("field1")
    public abstract String field1();

    @SerializedName("id")
    public abstract int id();

    @SerializedName("field2")
    public abstract String field2();

}

And my pojoItemList:

@AutoValue
public abstract class PojoItemList{

    public abstract List< PojoItem > itemList();

    public static TypeAdapter<PojoItemList> typeAdapter(Gson gson) {
        return new AutoValue_PojoItemList.GsonTypeAdapter(gson);
    }
}

I have AutoValueGsonFactory:

@GsonTypeAdapterFactory
public abstract class AutoValueGsonFactory implements TypeAdapterFactory {

    // Static factory method to access the package
    // private generated implementation
    public static TypeAdapterFactory create() {
        return new AutoValueGson_AutoValueGsonFactory();
    }
}

I'm using Retrofit with RxJava. I got this exception:

java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY

How can I setup my POJO to read JSON as an array of objects not as collection?

Answer 1

I could make it work by the end with/without RxJava Here are two ways:

To make it clear I will provide API and complete Retrofit code used to achieve that goal:

AppApi:

public interface AppApi {
    @GET("path/path")
    Observable<List<PojoItem>> getItemsbyRxJava();


    @GET("path/path")
    Call<List<PojoItem>> getItemsbyRetrofit();
}

1. Solution with RxJava:

   GsonConverterFactory gsonConverterFactory = GsonConverterFactory.create(new GsonBuilder().registerTypeAdapterFactory(AutoValueGsonFactory.create()).create());
   OkHttpClient.Builder httpClient = new OkHttpClient.Builder();
   Retrofit retrofitClient = new Retrofit.Builder()
           .baseUrl("http://[domain]/path/")
           .addConverterFactory(gsonConverterFactory)
           .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
           .client(httpClient.build())
           .build();
   
   AppApi appApi = retrofitClient.create(AppApi.class);
   
   appApi.getItemsbyRxJava()
           .subscribeOn(Schedulers.computation())
           .observeOn(AndroidSchedulers.mainThread())
           .subscribe(new Subscriber<List<PojoItem>>() {
               @Override
               public void onCompleted() {
                   Log.d(TAG, "completed");
               }
   
               @Override
               public void onError(Throwable e) {
                   Log.e(TAG, e.getMessage());
               }
   
               @Override
               public void onNext(List<PojoItem> list) {
                   for (PojoItem pojoItem : list) {
                       Log.d(TAG, pojoItem.field1() + "," + pojoItem.field2());
                   }
               }
           });
   

2. Solution with Retrofit only:

   OkHttpClient.Builder httpClient = new OkHttpClient.Builder();
   Retrofit retrofitClient = new Retrofit.Builder()
           .baseUrl("http://[domain]/path/")
           .addConverterFactory(GsonConverterFactory.create())
           .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
           .client(httpClient.build())
           .build();
   AppApi appApi = retrofitClient.create(AppApi.class);
   Call<List<PojoItem>> call = appApi.getItemsbyRetrofit();
   call.enqueue(new Callback<List<PojoItem>>() {
       @Override
       public void onResponse(Call<List<PojoItem>> call, Response<List<PojoItem>> response) {
           for (PojoItem pojoItem : response.body()) {
               Log.d(TAG, pojoItem.field1() + "," + pojoItem.field2());
           }
       }
   
       @Override
       public void onFailure(Call<List<PojoItem>> call, Throwable t) {
           Log.e(TAG, t.getMessage());
       }
   });
   

I hope that would be helpful to someone

Good luck,'.